执行检查java.lang.Double的相等方法 [英] Performant way to check java.lang.Double for equality
问题描述
我理解
double a = 0.00023d;
double b = 0.00029d;
boolean eq =(a == b);
很慢。
m使用
double epsilon = 0.00000001d;
eq = Math.abs(a-b) epsilon;
问题是 Infinitest
表示考试时间太长。
其他信息
是硬编码,因为它是期望值,
b
由
// fyi:current = int,max = int
public double getStatus()
{
double值= 0.0;
if(current!= 0&& max!= 0)
value =((double)current)/ max;
返回值;
}
更新
java.lang.Double会这样。
public boolean equals(Object obj){
return(obj instanceof Double)
&& (doubleToLongBits(((Double)obj).value)==
doubleToLongBits(value));
}
因此可以假设这是最佳做法。
JUnit有一个方法检查 Double
/ p>
Assert.assertEquals(0.00023d,0.00029d,0.0001d);
请参阅此API文档。
如评论,JUnit实际上最可能比比较手动与给定增量慢。 JUnit首先执行 Double.compare(expected,actual)
后跟(如果不等于) Math.abs(expected - actual)< =希望这个答案对于没有意识到JUnit实际上提供了一个不精确的方法的人有用
Double / code>等同测试。
What is the most performant way to check double values for equality.
I understand that
double a = 0.00023d;
double b = 0.00029d;
boolean eq = (a == b);
is slow.
So I'm using
double epsilon = 0.00000001d;
eq = Math.abs(a - b) < epsilon;
The problem is that Infinitest
is complaning about tests taking too much time. It's not a big deal (1 sec top), but it made me curious.
Additional info
a
is hard coded since it's the expected value, b
is computed by
// fyi: current = int, max = int
public double getStatus()
{
double value = 0.0;
if (current != 0 && max != 0)
value = ((double) current) / max;
return value;
}
Update
java.lang.Double does it that way
public boolean equals(Object obj) {
return (obj instanceof Double)
&& (doubleToLongBits(((Double)obj).value) ==
doubleToLongBits(value));
}
so one could assume that is the best practice.
JUnit has a method of checking a Double
for 'equality' with a given delta:
Assert.assertEquals(0.00023d, 0.00029d, 0.0001d);
As noted in the comments, JUnit actually most likely is slower than comparing manually with a given delta. JUnit first does a Double.compare(expected, actual)
followed (if not equal) by a Math.abs(expected - actual) <= delta
.
Hopefully this answer still is useful for people not aware that JUnit actually provides a way for inexact Double
equality testing.
这篇关于执行检查java.lang.Double的相等方法的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!